1. Field of the Invention
The present invention relates generally to distance measurement and, more particularly, to a system and method for distance measurement using harmonic signals.
2. Introduction
Wireless communication devices have been used to calculate distance measurements between two locations. In one method, known as the light wave method, a receiver is used to detect a laser signal that has been reflected off of an object. This method is limited, however, because it requires a direct line of sight to the object. Moreover, this method is limited to the calculation of distances to the surfaces of objects or structures.
In another method, radio frequency transmissions are used. This radio frequency method has the advantage of penetrability in that all points on a site are locatable, even points that are hidden from view. In this process, an interrogating device would send a first signal to a responding device, which would then reply (ideally with virtually zero delay) with a second signal back to the interrogating device. In one implementation the time of flight of the signal can be used to extrapolate a distance measurement. Here, the time of flight would represent the span of time between the sending of the first signal and the receipt of the second signal. Various limitations exist in this technique, such as the minimization of the delay at the responding device before a signal is returned to the interrogating device, or the difficulty in accurately determining transmission times at either device. Indeed, in some embodiments, three transmitting devices are needed to determine the location of the responding device.